Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
prae-trunco, āre, v. a., to cut off before or in front, to cut off, clip (Plautin.): collos (for colla) tergoribus, Plaut. Capt. 4, 3, 2: linguam alicui, id. Mil. 2, 3, 47.